NATURE OF THE DISEASE 



the epidemic character ; then, with the commencement 

 of the rainy season, it gradually diminishes again, and 

 reaches its lowest level towards the end of this and 

 the commencement of the cold weather. This same 

 character is observed in countries in which cholera is 

 not endemic, and which remain free from it for years, 

 e.g. Syria, Egypt, and European States. Cholera im- 

 ported into these areas gradually and steadily works 

 itself up into an epidemic, and equally gradually 

 again declines, the summer and spring being the most 

 favourable seasons in which it thus becomes epidemic. 

 During autumn, and towards the winter, the cases 

 become less numerous and milder, and as such may 

 occur as isolated cases all through the winter. 

 Towards spring they become again more numerous 

 and more severe, and in spring may cause a 

 recrudescence of the epidemic. Scarlet fever, diph- 

 theria, and typhoid fever are other well-known 

 instances in which acute endemic infectious disorders 

 during certain seasons show marked exacerbations. 

 In grouse disease the month of April, and the com- 

 mencement of May, are the times in which the 

 disease, as a rule, gradually by numbers and inten- 

 sity (fatal cases) becomes conspicuous. During the 

 end of May and the commencement of June it is at 

 its height, and then again declines during July ; but 

 fatal cases occur also during August, September, 



